Development and Evaluation of a Low-cost Custom-built OSLD Annealer: Application to Eye Lens Dosimetry

The International Commission on Radiological Protection (ICRP) has imposed a new limit to eye lens dose (ICRP 118), which has resulted in an absence of practical and reusable eye lens dosimetry solutions. Optically stimulated luminescence dosimeters (OSLDs) made of Al2O3:C, have become an area of interest because of their sensitive nature, small size, and non-destructive reading. Traditionally, the personal dose equivalent Hp(0.07) is frequently used as a proxy for eye lens dose Hp(3) when dosimeters are worn in the vicinity of the eye. Reliable multiple uses of OSLDs require optical annealing to be effective and reproducible in fully erasing any residual signals from the preceding measurement cycle. This study presents the design, construction, and evaluation of a low-cost, custom-built LED-based optical annealer developed for Landauer InLight OSLDs, focusing on eye lens dosimetry in beta and photon radiation fields. A microcontroller controls high-intensity ice blue LEDs that are utilized in the annealer to ensure uniform and repeatable optical bleaching. OSLDs were irradiated under a range of standardized photon and beta fields and annealed immediately after readout. The depletion of signals was monitored at regular intervals to determine the bleaching kinetics of all four windows of the dosimeter that represent Hp(10), Hp(3), Hp(0.07), and beta dose. The findings show that there has been a consistent exponential signal decay since the onset of the process, following first-order kinetics, with the rate constants ranging from 0.10 to 0.31 min-1 and the corresponding half-times being 2.2-6.9 minutes. Bleaching starts with a quick initial phase that removed >90% of the signal in 20 minutes with the depletion of shallow traps, followed by a slower phase that was related. This system enables reliable OSLD reuse for eye lens and skin dose monitoring and supports broader implementation of Hp(0.07)-based OSL dosimetry in occupational radiation protection.